The present disclosure relates to collection of waste toner in an image forming apparatus that performs printing using toner. In particular, the present disclosure relates to a fullness of a waste toner container detection device for a waste toner collection container.
In general, an image forming apparatus (such as a printer, a multifunction peripheral, a copier, or a facsimile machine) using toner and an electrophotographic method performs printing by forming a toner image on a photoreceptor drum, transferring the toner image onto a paper sheet, and fixing the toner image onto the paper sheet. Then, residual toner remaining on the photoreceptor drum without transferred is collected as waste toner. Further, a waste toner container for storing the waste toner may be disposed. When waste toner is continuously sent to the waste toner container despite the waste toner container is full, the waste toner may overflow and contaminate the inside of the image forming apparatus. In addition, when waste toner is continuously sent to the waste toner container despite the waste toner container is full, a large force may be applied to members for conveying waste toner (e.g. conveying screw and a conveying tube). As a result, members may be broken. Therefore, there is known a fullness detection device for detecting fullness of the waste toner container as follows.
For instance, there is known a waste toner fullness detection device including a waste toner collection container and a photosensor. The waste toner collection container includes a collection opening formed on a top surface of a book type storage portion for storing waste toner, so as to collect waste toner dropping to the storage portion, and a detection slit formed below the collection opening to protrude outward from the storage portion in such a manner that the center thereof is shifted from the waste toner dropping center in the collection opening, so that the waste toner level goes upward gradually along with increase of the waste toner stored in the storage portion. The photosensor detects the waste toner in the detection slit from outside of the waste toner collection container.
In this way, there is a case where the photosensor detects that waste toner is stored up to a certain level so that fullness of the waste toner container is detected. For instance, an optical sensor (a light emitting and a light receiving portion) sandwiches an upper end portion (neck portion) of a waste toner container having a certain transmittance, and transmitting light intensity is recognized on the basis of an output value of the light receiving portion. Because the waste toner interrupts light when the waste toner container becomes full, the light receiving portion cannot receive the light from the light emitting portion. For instance, it is determined that the waste toner container is full when the output value from the light receiving portion indicates that the light receiving portion receives little light when light emitting portion emits light.
The part of the waste toner container that transmits the light of the optical sensor is contaminated by the waste toner. In addition, the waste toner container is made of resin, and hence transmittance thereof is varied among individual waste toner containers. In addition, there is also a position error when disposing the optical sensor. In addition, there is also a position error when attaching the waste toner container. Because of these reasons, it is necessary to prevent a detection error even when worst conditions occur, by securing that the light from the light emitting portion reaches to the light receiving portion when the waste toner container is not full. Therefore, for example, when the fullness detection of the waste toner container is performed by using the optical sensor, maximum permissible rating power is supplied to the optical sensor considering worst conditions. In other words, the light emitting portion is driven to emit light at maximum intensity.
However, when the light emitting portion is always driven to emit light at maximum intensity (amount of luminescence) while the fullness detection of the waste toner container is performed, there is a case where the light intensity is higher than necessary. In other words, there is a case where non-fullness can be detected even when the light intensity of the light emitting portion is reduced to be lower than the maximum light intensity. Therefore, there is a problem that because the light emitting portion is driven at light intensity higher than a value necessary for detecting whether or not the waste toner container is full, for example, power is wastefully consumed, and life of a light emitting element of the light emitting portion is shortened.
Here, as to the known waste toner fullness detection device described above as an example, there is studied a position and the like of the detection slit. However, there is no description about light intensity of a light source of a photosensor 27. In addition, when the light source is always driven to emit light at light intensity lower than the maximum light intensity, there may occur a detection error such that fullness is detected though the waste toner container is not actually full, which causes an accuracy problem.